Working principle of EX-JDM1 explosion-proof digital anemometer

The EX-JDM1 explosion-proof digital anemometer is a kind of speed measuring instrument that converts the flow rate signal into an electrical signal, and can also measure the temperature or density of the fluid. The principle is that a thin metal wire heated by electricity is placed in the airflow, and the heat dissipation in the airflow is related to the flow rate, and the heat dissipation causes temperature changes to cause resistance changes, and the flow rate signal is converted into an electrical signal. It has two working modes: ① constant current type. The passing current is kept constant. When the temperature changes, the resistance changes, so the voltage at both ends changes, thereby measuring the flow rate; ② constant temperature type. The temperature remains unchanged, such as 150°C, and the flow rate can be measured according to the current required to be applied. The constant temperature type is more widely used than the constant current type. The length is generally in the range of 0.5 to 2 mm, and the diameter is in the range of 1 to 10 μm. The material is platinum, tungsten, or platinum-rhodium alloy. If a very thin metal film replaces the metal wire, it is a hot film anemometer. Its function is similar to the hot wire, but it is mostly used to measure the flow rate of liquid. In addition to the ordinary single-wire type, it can also be a combined two-wire type or three-wire type to measure the speed component in various directions. The output electrical signals are amplified, compensated, and digitized and then input into the computer, which can improve the measurement accuracy, automatically complete the data post-processing process, and expand the speed measurement function, such as the simultaneous completion of instantaneous value and time average, closing velocity and partial velocity, turbulence and Measurement of other turbulence parameters. Compared with the pitot tube, the anemometer has the advantages of small probe volume and small interference to the flow field; fast response, can measure unsteady flow rate; can measure very low speed and so on.

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